Pulverulent fuel



Patented Sept. 22, 1942 UNITED STATES PATENT GE FE'QE PULVERULENT FUELWilliam Hennicke, Mannheim, Germany; vested in the Alien PropertyCustodian No Drawing. Application August 31, 1938, Serial The presentinvention relates to a process of improving pulverulent fuels.

Pressure extracts of mineral or brown coals, which are to be used aspulverulent fuels and motor fuels, frequently have the objectionableproperty of softening even by slight heating and this results indeposits and stoppages in the supply pipes and nozzles and in thecylinders of motors and engines.

I have now found that the softening point of the said pressure extractsis raised by treating them with oxygen or gases containing the same atelevated temperatures but below their ignition point. The temperaturesto be used depend on the nature of the substances to be treated orreacted and the nature of the treatment and may be between 100 and 600C., for example in the case of the action of hot combustion gases whichstill contain oxygen on a pressure extract of mineral coal a temperaturebetween 300 and 500 C. is suitable. The procedure may be that a suitablefuel, as for example illuminating gas, is burned, the necessarytemperature established by the addition'of further air and the mixtureof combustion gases and air brought into contact with the material to betreated. As a reaction vessel it is suitable to use rotary tubes, tubesprovided with conveyor means, tower-like wide vessels in which thematerial is whirled up by the gas containing oxygen, or apparatus of asimilar kind. By the said treatment, the oxygen content of the fuel isappreciably increased and its softening point reduced to such an extentthat fuel dust treated in the said manner remains entirely pulverulentuntil its combustion and does not give rise to trouble by reason ofstoppages or soiling of the conveyor or distributing means. The nitrogencontent is not increased and the ignition point is not lowered or onlylowered to a negligible extent. A more marked. lowering of the ignitionpoint may only occur in some cases when prolonged for a very long time.

When the height of the ignition point is of no importance in thesubsequent use of the fuel, as for example in the case of a dust firing,the said treatment is sufiicient. On the other hand, for example whenthe fuel is to be used in a dust motor, if the fuel still ignites at toohigh a temperature, there may be carried out, in addition to thetreatment with oxygen, also a treatment with nitric acid or nitrousgases, as for example according to the copending application Ser. No.163,386 now U. S. Patent 2,208,514 dated the oxygen action is:

July 16, 1940. This treatment may be carriedout before or simultaneouslywith the oxygen treatment but preferably after the same. The heatimparted to the powder by the treatment with oxygen may be utilized ifdesired for the aftertreatment with nitric acid. In some cases it mayalso be preferable to cause the oxygen to act in only so. mild. a.manner that the softening point is not brought completely to the desiredvalue, as for example only to 350 C., the softening point and ignitionpoint only being changed in the desired manner by a subsequent nitricacid treatment. In any case considerably less nitric acid is requiredthan in the case of a fuel not previously treated with oxygen.

Another modification of the treatment with a view to increasing thesoftening point and reducing the ignition point consists in treatingpart of the pulverulent pressure extract with oxygen or gases containingthe same at elevated temperature, and another part with nitric acid oroxides of nitrogen and mixing the resulting products with each other.The height of the ignition point is dependent on the mixing proportions.For example an addition of from 25 to 30 parts of a fuel of low ignitionpoint which has been treated with nitric acid or oxides of nitrogen toparts of a fuel of high ignition point which has been treated withoxygen is sufiicient to obtain a mixture having a useful ignition point.Similarly a part of the residues remaining in the distillation of browncoal pressure extracts with steam or in the treatment with selectivesolvents may be treated with nitric acid and another part with gasescontaining oxygen and the resulting products mixed with each other insuitable proportions. It is also possible to prepare mixtures of mineralcoal extracts treated with oxygen and distillation residues of browncoal pressure extracts treated with nitric acid. The ignition point ofthe part of the fuel which has only been treated with oxygen is reducedto a specially marked degree by incorporating therewith fuel treatedwith nitric acid directly after treatment and while still in the moiststate, the mixture then being dried. Apparatus known for the purpose maybe used for the mixing, as for example spirals, drums, ball mills andthe like.

The ignition point of the pulverulent fuels or motor fuels of highmelting point thus obtained can be reduced still further and furtherimprovements can be obtained by adding thereto small amounts of liquidfuels.

Among suitable liquid fuels there may be mentioned for example motorfuels, such as gas oils,

of liquid additional substance, but in most cases 7 from 3 to 10 percent are sufiicient to reduce the ignition point considerably but toretain a state in which the powder can still be conveyed withoutdifliculty, does not stick and form lumps and melts only at such a hightemperature that no trouble can occur.

The mixing may be carried out in all apparatus known for the purpose,such as mixing worms, ball mills, drums and the like; the solidsubstances and liquid substances may be mixed directly with each other,or the solid substances may be sprayed with the liquid substances withthe aid of nozzles, or the liquid substances may be vaporized andallowed to condense on the solid substances.

The process is used in particular for extracts of mineral and browncoals obtained under pressure with the use of solvents, moreparticularly solvents giving oiT hydrogen, if desired with thesimultaneous pressure of hydrogen with or without the use of catalysts;furthermore for substances obtained from the pressure extracts forexample by distillation, extraction, splitting up by mechanical means orin other ways and having a higher melting point than the originalextracts.

The following examples will further illustrate how the present inventionmay be carried out in practice, but the invention is not restricted tothese examples. The parts are by weight.

Example 1 Into one end of a tube provided with a conveyor worm there areintroduced per hour 100 parts of a finely powdered pressure extractobtained from mineral coal. At the opposite end such an amount ofilluminating gas is burned that the combustion gases, after the additionof 40 parts of air, have a temperature of 450 C. This gas mixture is ledover the powdered pressure extract. The temperatures of the effluent gasand the withdrawn mass depend to a large extent on the construction ofapparatus used. They may amount to 120 and 240 centigrade. The treatedfuel has the following characteristics as compared with the untreatedmaterial:

For further lowering of the ignition point, a treatment with nitric acidmay be carried out, 4.2 parts of nitric acid (calculated as 100 percent) being used for 100 parts of oxidized extract. The lower ignitionpoint of the final product then lies at 280 C. An extract not havingundergone any pretreatment yields under the same conditions a productwhich ignites at 260 C, but which softens even at from 380 to 385 C.

Example 2 A part A of a pressure extract obtained from mineral coal istreated according to Example 1 at 500 C. for 20 minutes with combustiongases of illuminating gas containing oxygen. The temperature of thewaste gases amounts to 220 C. and that of the withdrawn mass to 200 C.An-

other part B is treated according to application Ser. No. 163,386 withnitric acid (0.40 liter of HNO3 per kilogram of extract with 850 gramsof HNO3 per liter of acid) and dried to a water content of 1.2 per cent.Mixtures of the resulting products A1 and B1 are prepared. The ignitionpoints of these mixtures may be seen from the following table:

Mixing proportions Ignition point A] B] Example 3 Mixing proportionsIgnition point 7 A] O} Example 4 A finely powdered extract obtained bypressure extraction of mineral coal is treated in a rotary tubularfurnace in counter-current with combustion gases of illuminating gascontaining an excess of air according to Example 1. The temperature ofthe introduced gas is 500, that of the outgoing gas is 220 and that ofthe mass withdrawn is 200 C. The mass is in contact with the gases for20 minutes. The material withdrawn has a softening point above 500 andan ignition point of 438 C. The resulting product (A) is mixed invarious proportions with different liquid motor fuels in a ball mill,the relative proportions and the ignition points of the mixtures beinggiven in the following table:

Parts Ignition Numby Parts by weight of additional point her weightsubstance of of A mixture 95 90 5 of 316 92 4 of gas oil and 4 ofbenzene .1 280 94 3 of gas oil and 3 of acetaldehyde 234 95 4 of gas oiland l of paraldehyde.. 268

free oxygen at a temperature below their ignition point and part with asubstance selected from the group consisting of nitric acid and nitricgases so that the initial material retains its loose pulverulentcondition and nitrogen and oxygen are incorporated into the coalextracts, and mixing the products thus obtained with each other.

WILLIAM HENNICKE.

